Combined Effect of Thermal and Mechanical Stresses on the Viscoelastic Properties of a Composite Material for Space Structures

Abstract

Thermal ageing of polymer-matrix composite materials of any long-life spacecraft in LEO involves evolution of mechanical, thermophysical and morphological properties, especially if the structure operates under external mechanical stress like bending. Behavior of KMU-4l carbon/epoxy composite material under combined effect of thermal profiles and static mechanical loading has been studied in a simulated LEO space environment. Thermal cycling was performed on specimens under bending stress reaching 30.4 % of the material ultimate strength. Specimens subjected to combined thermal and mechanical fatigue were examined in a series of 4 intermediate points with a maximum of 120 cycles.The Dynamic Mechanical Thermal Analysis has been employed to follow the global thermomechanical response of KMU-4l composite. The degradation produced was detected by moisture diffusion analysis, the crack density was estimated at the edges of the specimens using a scanning electron microscope. Effects such as the temperature dependence of material properties and matrix post-curing phenomena are also discussed. The results are compared with the appropriate data obtained on specimens of KMU-4l exposed for up to 1501 days to LEO space environments onboard SALYUT and MIR orbital stations.KeywordsThermal CycleDynamic Mechanical Thermal AnalysisThermal AgeingMoisture DiffusionSpace DebrisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.